Portable, refrigerant recovery unit

ABSTRACT

A portable, refrigerant recovery unit for transferring refrigerant from a refrigeration system to a storage tank. The unit includes two, opposed piston heads rigidly attached to respective piston rods that extend along a common fixed axis and are rigidly attached to a scotch yoke arrangement. In operation, incoming refrigerant is simultaneously and continuously directed to the opposing piston heads wherein the forces of the pressurized refrigerant on them counterbalance one another. The flow path of the refrigerant is designed to be isolated from the piston rods and drive mechanism to avoid any exposure to any contaminants in the refrigerant. However, to the extent the undersides of the piston heads and portions of the piston rods may be so exposed, a chamber is provided adjacent each piston underside to capture or collect any contaminants and direct them harmlessly back through one-way exhaust lines into the incoming refrigerant lines.

BACKGROUND OF THE INVENTION

1. Field of the Invention.

This invention relates to the field of portable, refrigerant recoveryunits,

2. Discussion of the Background.

Portable, refrigerant recovery units are primarily used to transferrefrigerant from a refrigeration system to a storage tank. In thismanner, the refrigerant can be removed from the system and captured inthe tank without undesirably escaping into the atmosphere. Neededrepairs or other service can then be performed on the system.

Such recovery units face a number of problems in making the transfer ofthe refrigerant to the storage tank. In particular, the initialpressures of the refrigerant in the system can be quite high (e.g.,100-300 psi or more). These pressures can exert significant forces onthe components of the unit including the pistons and drive mechanism. Insome cases, the initial force may even be high enough to overpower thedrive mechanism of the recovery unit and prevent it from even starting.In nearly all cases, the forces generated by the incoming pressurizedrefrigerant during at least the early cycles of the recovery operationare quite substantial and can be exerted in impulses or jolts. Theseforces can easily damage and wear the components of the unit if notproperly handled.

In some prior designs, attempts have been made to minimize the forcesexerted on the piston by exposing both sides of the head of the pistonto the pressurized refrigerant. However, nearly all of these priordesigns result in exposing not only the underside of the piston head tothe refrigerant but also the piston rod and drive mechanism (e.g.,crankshaft). Because the refrigerant typically has oil and othercontaminants (e.g., fine metal particles) in it, the exposed piston rod,crankshaft, and other parts of the recovery unit can become prematurelyworn and damaged, particularly at their seals and bearings.

In other prior arrangements that do not expose these parts of the unitto the refrigerant, efforts have been tried to minimize the wear anddamage to the drive mechanism (e.g., crankshaft bearings) from therefrigerant forces by operating another piston along the crankshaft at180 degrees out of phase. However, these arrangements still drive thepiston rods eccentrically about the axis of the crankshaft and out ofalignment with each other. In most cases, they also pivotally mount thepiston heads to the piston rods (e.g., with wrist pins). Although theforces of the pressurized refrigerant on the crankshaft are somewhatoffset in such arrangements, the eccentrically mounted and unalignedpiston rods still apply unbalanced stresses to the crankshaft.Additionally, the forces of the pressurized refrigerant are still borneby the pivot arrangement between the head and rod of each piston. Thepivot arrangement in particular can then wear leading to irregularoperation of the piston and seal leakage. Eventually, the pivotarrangement may even fail altogether.

With these and other problems in mind, the present invention wasdeveloped.

SUMMARY OF THE INVENTION

This invention involves a portable, refrigerant recovery unit fortransferring refrigerant from a refrigeration system to a storage tank.The recovery unit includes two, opposed piston heads rigidly attached torespective piston rods that extend along a common fixed axis. The pistonrods in turn are rigidly attached to the yoke member of a scotch yokearrangement. The scotch yoke arrangement translates rotational motionfrom a driving mechanism into reciprocal movement of the yoke member andrigidly attached piston rods and piston heads along the common fixedaxis.

In operation, incoming refrigerant from the system is simultaneously andcontinuously directed to the opposing piston heads wherein the forces ofthe pressurized refrigerant on them counterbalance or neutralize oneanother. The drive mechanism of the unit can then reciprocate thepistons independently of the size of any forces generated on them by theincoming refrigerant. The flow path of the refrigerant is also designedto be isolated from the piston rods and drive mechanism to avoid anyexposure to any contaminants in the refrigerant. However, to the extentthe undersides of the piston heads and portions of the piston rods maybe so exposed, a chamber is provided adjacent each piston underside tocapture or collect any contaminants and direct them harmlessly backthrough one-way exhaust lines into the incoming refrigerant lines. Asingle piston embodiment is also disclosed. Details of the scotch yokearrangement are additionally disclosed including a two-piece slidemechanism mounted about a cylindrical crank pin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the portable, refrigerant recovery unitof the present invention.

FIG. 2 illustrates a typical operating arrangement in which the recoveryunit is used to transfer refrigerant from a refrigeration system to astorage tank.

FIG. 3 is a schematic showing of part of the operating arrangement ofFIG. 2.

FIGS. 4-6 are sequential views of the operation of the opposing pistonsof the compressor of the present invention.

FIG. 7 is a view of the pistons at the outset of a hookup to therefrigeration system of FIG. 2 in which the pressures of therefrigeration system and storage tank are being equalized prior to thestart up of the compressor.

FIG. 8 is a perspective view of the compressor.

FIG. 9 is a view taken along line 9-9 of FIGS. 6 and 8.

FIG. 10 is an exploded view of the drive mechanism for the compressor.

FIG. 11 is a cross-sectional view of a single piston embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates the portable, refrigerant recovery unit 1 of thepresent invention. In a typical operating arrangement as shown in FIG.2, the unit 1 is used to transfer refrigerant from the refrigerationsystem 2 to the storage tank 4. This basic operating arrangement isschematically illustrated in FIG. 3. In it, refrigerant from therecovery system 2 of FIG. 2 is being delivered through the line 6 (FIGS.2 and 3) to the incoming lines 7, 7′ of the recovery unit 1 (FIG. 3).The lines 7,7′ as illustrated are respectively connected to the inlets9,9′ of the compressor 11 of the recovery unit 1. From the compressor 11in FIG. 3, the refrigerant is passed through outlets 13,13′ to the lines15,15′ on which condensers 17,17′ are mounted and then through line 18to the storage tank 4 of FIG. 2,

The compressor 11 of the recovery unit 1 as best seen in FIG. 4 hasopposing piston heads 21,21′ respectively rigidly attached to pistonrods 23,23′. The piston rods 23,23′ in turn extend along a common fixedaxis 25 and are rigidly attached to the side pieces 27,27′ of the yokemember 29. The piston rods 23,23′ in FIG. 4 extend in oppositedirections from the yoke side pieces 27,27′ along the common fixed axis25. The yoke member 29 as explained in more detail below is part of ascotch yoke arrangement 31. The scotch yoke arrangement 31 in thisregard serves to translate rotational motion from a driving mechanismdiscussed later into reciprocal movement of the yoke member 29 andrigidly attached piston rods 23,23′ and piston heads 21,21′ along thecommon fixed axis 25.

Each piston head 21,21′ in FIG. 4 is slidably and sealingly received ina cylinder 33,33′ having an inner, cylindrical side wall with a firstportion 35,35′ and an end wall 37,37′. As shown in FIG. 4, each end wall37,37′ has an inlet 39,39′ and outlet 41,41′ with respective one-wayvalves 43,43′ and 45,45′ therein. Each piston head 21,21′ in turn has anouter surface 47,47′ opposing the end wall 37,37′ to define a chamber49,49′ with the end wall 37,37′ and the first side wall portions 35,35′of each chamber 49,49′. These substantially mirror-image, twinarrangements are preferably identical in size and in particular, thecircular areas of the outer surfaces 47,47′ of the piston heads 21,21′are preferably the same (e.g., about one inch in diameter).

The reciprocating piston rods 23,23′ move the respective piston heads21,21′ along the common fixed axis 25 relative to the cylinder end walls37,37′ between first and second positions. The piston heads 21,21′ inthis regard oppose one another and are operated 180 degrees out of phasewith each other. More specifically, as the piston 21 of FIG. 4 forexample is moved to its first position (see FIG. 5), the volume of thechamber 49 is expanded to receive refrigerant from the refrigerationsystem 2 of FIG. 2 through the common line 6 (FIGS. 2 and 3) andincoming line 7. At the same time, the opposing piston head 21′ is beingmoved to its second position of FIG. 5 to contract the volume of thechamber 49′ of FIG. 4 to drive the refrigerant out of the chamber 49′into line 15′. The process is then reversed to move the aligned pistonheads 21,21′ to the position of FIG. 6. In the contracted position ofeach piston head (e.g., see 21′ in FIG. 5), the substantially parallelpiston surface 4T and the end wall 37′ of FIG. 4 preferably abut and areflush with one another for maximum compression (e.g., 300:1 or more). Asshown in FIGS. 4-6, the piston heads 21,21′ and piston rods 23,23′during their movement between the respective first and second positionsare constrained to move symmetrically along the common fixed axis 25.

In operation, the refrigerant in the refrigeration system 2 to berecovered is normally at an initial pressure above atmospheric. In mostcases, the pressure of the refrigerant will be well above atmospheric(100-300 psi or more). In contrast, the initial pressure in the storagetank 4 can vary from below atmospheric to above atmospheric dependingupon how nearly empty or full the tank 4 is. As for example, the storagetank 4 prior to the start of a recovery operation may have beenevacuated below atmospheric to remove air so as not to contaminate therefrigerant to be recovered. On the other hand and if the storage tank 4is partially full (e.g., from a previous operation), the tank 4 may beat a pressure above atmospheric or even above the pressure of therefrigerant to be recovered from the refrigeration system 2 of FIG. 2.To the extent the initial pressure of the storage tank 4 is above theinitial pressure of the refrigeration system 2, the outlet valves 45,45′of the chambers 49,49′ in FIG. 4 will remain closed. However, to theextend the initial pressure of the storage tank 4 at hookup is below thepressure of the refrigerant in the refrigeration system 2, both pairs ofinlet and outlet valves 43,45 and 43′,45′ will be opened as shown inFIG. 7. Refrigerant will then flow uninhibited from the refrigerationsystem 2 to the storage tank 4 until the pressures equalize and thevalves 43,43′,45,45′ close.

Thereafter, the operation of the compressor 11 of the recovery unit 1 asillustrated in FIGS. 4-6 will be needed to transfer refrigerant from therefrigeration system 2 to the storage tank 4.

During the initial cycles of operation of the compressor 11 as indicatedabove, the refrigerant in the refrigeration system 2 normally is stillabove atmospheric. In most cases as also previously discussed, theincoming refrigerant will be well above atmospheric (e.g., 100-300 psior more). Such high pressures if not properly handled can easilygenerate forces great enough to damage the components of the compressor11 and lead to premature failure. In particular and if not properlyhandled, the initial force at hookup may even be high enough tooverpower the driving mechanism of the compressor to the point that itcannot be started. To prevent this as explained in more detail below,the piston heads 21,21′ of the present invention are mounted in anopposing configuration wherein the forces generated on them by theincoming, pressurized refrigerant are counterbalanced or neutralized.Start up problems are essentially eliminated and any damage and wear dueto the high forces of the pressurized refrigerant during the initialcycles of operation are greatly reduced.

More specifically and looking first at only the half of FIG. 7 to theright of line A-A, the incoming refrigerant in line 7 of FIG. 7 isnormally at pressures well above atmospheric (e.g., up to 100-300 psi ormore). Such pressures will open the inlet valve 43 and instantaneouslyexert a force F on the outer surface 47 of the piston head 21. Thisforce F can be very significant and remain so during the initial cyclesof the recovery operation until the pressure of the incoming refrigerantis greatly reduced (e.g., to 50-75 psi or lower). The initial size ofthe force F as discussed above may even be high enough to overpower thedrive mechanism of the compressor 11 (were only the right piston head 21and piston rod 23 of FIG. 7 present) and prevent the compressor 11 fromstarting. Initially and until the pressure of the incoming refrigerantin such a design is significantly reduced, the applied force F (whichmay even be exerted in impulses or jolts) on the piston head 21, pistonrod 23, and the drive mechanism for the compressor 11 could easily leadto premature wearing and even failure. This is particularly true if thehigh pressure refrigerant is in a liquid phase. Eventually, the size ofthe force F would be reduced with each cycle of the piston head 21 asthe pressure of the incoming refrigerant falls and the refrigerant is ina gas or vapor phase. However, until the refrigerant pressure(regardless of phase) in such a design is significantly reduced (e.g.,to 50-75 psi or lower), each force F during each reciprocating cycle ofthe piston head 21 could damage and strain the components of thecompressor 11. Again, this is describing the case were only the rightpiston head 21 and piston rod 23 of FIG. 7 present. However, in thepreferred embodiment, the previously unbalanced force F on the pistonhead 21 on the right half of FIG. 7 at the outset and subsequent cyclicoperation of the recovery unit 1 is counterbalanced or neutralized by anopposing force F′ on the opposite piston head 21′. The potentiallydamaging effect of the incoming force F is thereby essentiallyeliminated. This is particularly true because the intermediate structureincluding the piston heads 21,21′ and piston rods 23,23′ are axiallyaligned along 25 and rigidly attached to one another. Further, the drivemechanism for the compressor 11 only needs to then provide adifferential force D (see FIG. 4) to reciprocate the piston heads 21,21′to compress the refrigerant in the respective chambers 49,49′ and drivethe refrigerant into the storage tank 4. In doing so, the drivemechanism of the compressor 11 does not have to overcome or compensatefor the forces F,F′ on the piston heads 21,21′ in FIG. 7 as theycounterbalance or neutralize one another. The drive mechanism for thecompressor 11 can thus be designed to provide a maximum pressure (e.g.,550 psi or more in the chambers 49,49′) without having to consider orcompensate for any effects of the incoming, refrigerant forces F,F′. Inmost cases, the compressor 11 can actually generate much higherpressures (750-1500 psi or more) but the operation of the unit 1 isnormally limited to a lower pressure (e.g., 550 psi) for safety toprotect the storage tank 4.

The isolation of the drive mechanism from the forces F,F′ isparticularly important because the operating fluid as discussed above istwo phase refrigerant. Consequently and usually unpredictably, theincoming refrigerant at any time may change phases and widely vary theforces F,F on the piston heads 21,21′. However, due to thecounterbalancing design of the present invention, the forces F,F′ at anysuch time on the piston heads 21,21′ are neutralized along the commonaxis 25. The drive mechanism for the compressor 11 is then essentiallyunaffected by the forces F,F′ and/or the conditions (e.g., pressure,temperature, phase) of the incoming refrigerant. The differential forceD provided by the compressor 11 in FIG. 4 will therefore be enough tomove the twin piston heads 21,21′ repeatedly through their cycles totransfer the refrigerant (regardless of its phase or state from therefrigeration system 2 to the storage tank 4.

Although the counterbalancing design of the preferred embodimentisolates the differential force D from the forces F,F′, the drivemechanism including the piston rods 23,23′ of the compressor 11 and thecomponents of the scotch yoke arrangement 31 must still be fairlystructurally substantial. This is the case because the forces F,F′(particularly during the initial operational cycles of the unit 1) muststill be borne by the opposing components of the compressor 11. Thisincludes the axially aligned piston heads 21,21′ and piston rods 23,23′as well as the yoke member 29 of the scotch yoke arrangement 31. In thisregard, it is again noted that these aligned and opposed members arerigidly attached and fixed to one another. This further enhances theirability to carry large loads including from the forces F,F′ without theundue damage and wear that might occur were these components not alignedand fixed relative to each other and not constrained to movesymmetrically along the common fixed axis 25.

In operation, the compressor 11 as shown in FIG. 4 provides thedifferential force D in a direction (e.g., to the left in FIG. 4) alongthe common fixed axis 25. Only the force D is illustrated in FIG. 4 forclarity because the opposing forces F,F of FIG. 7 as discussed abovecancel one another out. However, in driving the compressor 11 to theleft in FIG. 4, the differential force D does combine with the force Fof the pressurized refrigerant on the piston head 21 in that samedirection to create a second force (F+D). This second force is thengreater than the opposing first force F′ on the opposing piston head21′. The opposing piston head 21′ is thereby driven to the left in FIG.4 toward its contracted position of FIG. 5.

Stated another way, the incoming refrigerant at pressures aboveatmospheric in the lines 7,7′ to the chambers 49,49′ exerts first,opposing forces F,F′ on the outer surfaces 47,47′ of the piston heads21,21′. These opposing forces F,F′ are directed along the common fixedaxis 25. During the operating cycle as for example when piston head 21is moved from its contracted position of FIG. 6 back to its expandedposition of FIG. 5, the differential force D supplied by the scotch yokearrangement 31 adds to the force F on the piston head 21. This in turnserves to move the other piston head 21′ to its contracted position ofFIG. 5. The cycle is then repeated and is largely independent of anychanging conditions (pressure, temperature, phase) in the refrigerant orthe forces F,F′.

To aid in maintaining the forces F,F′ essentially the same, the incominglines 7,7′ as indicated above (FIG. 3) are in fluid communication witheach other and with the refrigerant in the line 6 from the refrigerationsystem 2 of FIG. 2. In this manner and even though the pressure of therefrigerant varies over time, it will always be the same in the incominglines 7,7′. Consequently, the inlet valves 43,43′ of the chambers 49,49′upstream of the inlets 39,39′ are simultaneously and continuouslyexposed to the same refrigerant pressure. The opposing forces F,F′generated by the incoming, pressurized refrigerant on the outer surfaces47,47′ of the opposing piston heads 21,21′ are then essentially alwaysthe same. It is additionally noted that the outgoing lines 15,15′ inFIG. 2 downstream of the outlet valves 45,45′ in each chamber outlet41,41′ are also in fluid communication with each other and the storagetank 4 through line 18.

In the counterbalancing design of the preferred embodiment, only thechambers 49,49′ and the flow paths to and from them are intended to beexposed to the refrigerant and its possible contaminants (e.g., oil,fine metal particles). In particular, the undersides or bottoms 51,51′of the piston heads 21,21′ in FIG. 4 are preferably designed not to beexposed to the refrigerant as are the drive mechanism including thepiston rods 23,23′ and the components of the scotch yoke arrangement 31.However, to the extent the undersides 51,51′of the piston heads 21,21′and portions of the piston rods 23,23′ may be so exposed, a chamber55,55′ is provided adjacent the respective piston undersides 51,51′ (seeFIG. 4) to capture or collect any contaminants and direct themharmlessly back through the one-way exhaust lines 61,61′ into theincoming refrigerant lines 7,7′. Should any contaminants so collect inthe chambers 55,55′, they are still isolated from reaching the morevulnerable components of the scotch yoke arrangement 31

More specifically, each piston head 21,21′ as indicated above and shownin FIG. 4 has an underside 51,51′ adjacent the piston rod 23,23′attached to the piston head 21,21′. The piston undersides 51,51′ extendabout the respective piston rods 23,23′ and outwardly of the commonfixed axis 25. The recovery unit in turn includes second end walls at53,53′ (FIG. 4) respectively opposing the undersides 51,51′ of thepiston heads 21,21′. The second end walls 53,53′ and piston undersides51,51′ along with the second side wall portions 57,57′ of the cylinders33,33′ (FIG. 4) then define respective, annular second chambers 55,55′.Exhaust lines 61,61′ are then provided as shown in FIG. 4 to extendbetween the respective second chambers 55,55′ and the respectiveincoming refrigerant lines 7,7′. Each exhaust line 61,61′ has a one-wayvalve 63,63′ in it to restrict flow therethrough to one direction fromthe respective second chambers 55,55′ to the respective incoming lines7,7′.

In operation, each reciprocating piston rod 23,23′ as discussed abovemoves the respective piston head 21,21′ along the common fixed axis 25relative to the respective first end wall 37,37′ of the cylinder 33,33′between first and second positions. In doing so, the volume of the firstor working chambers 49,49′ are respectively expanded and contracted.Conversely, the volume of the second chambers 55,55′ are thenrespectively contracted and expanded. The one-way valves 63,63′ in turnin the respective exhaust lines 61,61′ are then opened as the volume ofthe respective second chamber 55,55′ contracts and closed as the volumeof the respective second chamber 55,55′ expands (see FIGS. 5 and 6). Inthis manner and to the extent any refrigerant and/or contaminantscollect in the chambers 55,55′, they will be captured and directedharmlessly back through the one-way exhaust lines 61,61′ into theincoming refrigerant lines 7,7′ and out the discharge lines 15,15′. Theundesirable refrigerant and/or contaminants in this regard arepositively pumped into the incoming lines 7,7′ as the pressure in therespective, contracting second chambers 55,55′ exceeds the line pressureof 7,7′. To aid in discharging these undesirable fluids and with thecommon fixed axis 25 extending substantially horizontally as in FIG. 4,the inlet to each exhaust line 61,61′ preferably extends as shown fromeach second chamber 55,55′ substantially at the lowest location of thesecond chamber 55,55′ relative to the common fixed axis 25. Gravity canthen help in collecting and delivering the contaminants into the exhaustlines 61,61′ particularly at the start up of the recovery unit andduring its operation. The flow through the exhaust lines 61,61′ alsoserves to reduce the pressure load on the piston rod seals 54,54′ inFIG. 4 to further ensure that no contaminants pass thereby and that thescotch yoke arrangement 31 remains isolated from any such exposure. Inthis regard, the second end walls 53,53′ of the second chambers 55,55′(see FIG. 4) slidably and sealingly at 54,54′ receive the reciprocatingpiston rods 23,23′ therethrough. As discussed above, the piston rodseals at 54,54′ then aid in isolating the scotch yoke arrangement 31from the second chambers 55,55′ and their contents. It is noted that thefirst and second side wall portions 35,57 and 35′,57′ of each cylinder33,33′ in FIG. 4 are adjacent one another along the axis 25. Theseportions can be spaced from each other as shown or can overlap oneanother if desired. The piston undersides 51,51′ preferably have thesame annular area and are preferably parallel to the respective outerpiston surfaces 47,47′.

Referring to FIGS. 6 and 8-9, the drive mechanism for the compressor 11includes the motor 20 (FIG. 9) which rotates the shaft 22 about the axis24. The motor shaft 22 has a flattened upper portion 22′ and is attachedadjacent the counterweight C (FIGS. 8-9) by a set screw 26 (see againFIG. 9) to the crankshaft 28 of the scotch yoke arrangement 31. Thecrankshaft 28 (see also FIG. 10) has spaced-apart bearing portions32,32′ with cylindrical surfaces 34,34′ extending symmetrically aboutthe rotational axis 24 within the race bearings 36,36′ of FIG. 9. Acrank pin 38 (FIGS. 8-9) integrally extends between the bearing portions32,32′ and has a cylindrical surface 40 extending along and about theaxis 42. The circumference of each cylindrical surface 34,34′ about theaxis 24 is substantially larger than the circumference of thecylindrical surface 40 about the axis 42. This is in contrast to manyprior art designs in which the circumference of the crank pin oreccentric drive member is greater than the circumference of the adjacentbearing portion or portions.

In operation, the motor 20 (FIG. 9) rotates the motor shaft 22 andattached crankshaft 28 about the axis 24. This in turn rotates the crankpin 38 about the axis 24 with the axis 42 of the crank pin 38 alsomoving about the parallel axis 24. The rotating crank pin 38 in FIG. 9is received within the two, opposing slide pieces 44 of the scotch yokearrangement 31 (see also FIG. 5). The separate, slide pieces 44,44′(FIG. 5) are confined and mounted by balls 46 to slidingly move relativeto the yoke pieces 27,27′ along the vertical axis 48. The vertical axis48 in the orientation of FIG. 5 passes symmetrically through the middleof the yoke member 29. In this manner and as the motor shaft 22 andcrankshaft 28 are rotated about the axis 24 (FIG. 9), the offset crankpin 38 and its axis 42 are rotated about the axis 24.

The yoke side pieces 44,44′ of FIG. 5 are then moved up and downrelative to the axis 48, which motion in turn reciprocally moves theyoke member 29 and attached piston rods 23,23′ and piston heads 21,21′along the axis 25. The axes 24 and 42 of FIGS. 9 and 10 in this regardare substantially parallel to one another and substantiallyperpendicular to the axes 25 and 48 of FIG. 5. In this manner, thescotch yoke arrangement 31 thus translates rotation motion of thedriving members 22, 28, and 38 about the axis 24 in FIG. 9 to reciprocalmovement of the yoke member 29 and attached piston rods 23,23′ andpiston heads 21,21′ along the axis 25 in FIG. 5. The slide pieces 44,44′as shown in FIG. 5 abut one another about the crank pin 38 and needlebearing members or pins 50. In this regard, the abutting surfaces 52,52′of the pieces 44,44′ are preferably substantially parallel to eachother. Additionally, at least one of the surfaces 52,52′ in eachabutting pair and preferably both surfaces 52,52′ have a groove 56therein (see also FIG. 10). The groove 56 is in fluid communication withthe areas 58,58′ (FIG. 5) above and below the slide pieces 44,44′. Theneedle bearings 50 about the crank pin 38 are confined as shown betweenthe semi-cylindrical and inner facing surfaces 60,60′ of the pieces44,44′. In this manner and as the pieces 44,44′ slidingly move along theaxis 48 relative to the yoke member 29 in FIGS. 4-6, lubricant in theareas 58,58′ of FIG. 5 is forced or pumped through the grooves 56 to theneedle bearings 50. The crankcase or yoke housing members 75 in thisregard are substantially air tight to keep out dirt. This serves toenhance the pumping action on the lubricant as the volume of the areas58,58′ are contracted. Additionally, the outer surfaces 62,62′ of theslide pieces 44,44′ adjoining the surfaces 52,52′ (see FIG. 6) havedepressed or concave portions. These portions form respective pockets 65as illustrated in FIG. 6 adjacent the entry to each groove 56 to collectlubricant.

The pieces 44,44′ of the sliding mechanism as discussed above aremounted to move up and down (in the orientation of FIGS. 5 and 6) alongthe axis 48 relative to the yoke member 29. The actual motion is alongsemi-circles extending along each side of axis 48. Although the abuttingyoke side pieces 27,27′ as seen in FIG. 7 bear any large, opposingforces F,F that are generated by the pressurized refrigerant and isolatethe slide pieces 44,44′ from the forces F,F′, the movement of the crankpin 38 in FIGS. 4-6 still generates significant forces on the yoke sidepieces 27,27′. As for example, the compressor 11 may generate maximumpressures of 550 psi or more in the chambers 49,49′ driving therefrigerant out to the tank 4. To ameliorate or dissipate the highforces that can be generated between the driving slide pieces 44,44′ anddriven yoke side pieces 27,27′, a plurality of rows of the balls 46(FIGS. 6 and 10) are preferably provided. These balls 46 (see FIG. 6)are positioned between the inwardly and outwardly facing surfaces 64,64′of the respective pairs of yoke 27,27′ and slide 44,44′ pieces (see alsoFIGS. 9 and 10). Each surface 64,64′ preferably has at least two groovesor tracks 66,66′ (FIGS. 9 and 10) extending substantially perpendicularto the axis 25 of FIG. 6 with the balls 46 positioned therein. Thedriving force D of each slide piece 44,44′ is then spread over morecontact points between the surfaces 64,64′ to reduce potential wear anddamage. The plurality of balls 46 and tracks 66,66′ also helps tomaintain the alignment of the driving side pieces 44,44′ and driven yokemember 29.

In FIG. 11, a single piston 21″ embodiment is shown which is driven byessentially the same scotch yoke arrangement 31″ as 31 in the earlierembodiments. As in the earlier embodiments, the under surface 51″ of thepiston head 21″ adjacent the piston rod 23″ extends outwardly of andabout the fixed axis 25″ as shown in FIG. 11. The stub or rod R on theother side of the yoke member 29″ in FIG. 11 is rigidly attached to theyoke member 29″ and the movement of the rod

R like that of piston rod 23″ and piston head 21″ is confined to alongonly the fixed axis 25″. This is in a manner corresponding to theearlier, twin embodiments. Similarly, the piston head 21″, piston rod23″, and yoke member 29″ of FIG. 11 are rigidly attached to one another.

The embodiment of FIG. 11 like the earlier ones is provided with acorresponding first chamber 49″ within the cylinder 33″ defined by afirst side wall portion 35″ of the cylinder 33″, a first end wall 37″ ofthe cylinder 33″, and the outer piston surface 47″. The embodiment ofFIG. 11 then has a second chamber 55″ defined by the underside 51″ ofthe piston head 21″, the second side wall portion 57″ of the cylinder33, and the second end wall 53″. An exhaust line 61″ is then provided asshown in FIG. 11 to extend between the second chamber 55″' and theincoming refrigerant line 7′. The exhaust line 61″ has a one-way valve63″ in it to restrict flow therethrough to one direction from the secondchamber 55″ to the incoming line 7′. In operation, the reciprocatingpiston rod 23″ like the earlier embodiments moves the piston head 21″along the fixed axis 25″ relative to the first end wall 37″ of thecylinder 33″ between first and second positions. In doing so, the volumeof the first or working chamber 49″ is expanded and contracted.Conversely, the volume of the second chamber 55″ is then contracted andexpanded. The one-way valve 63″ in turn in the exhaust line 61″ isopened as the volume of the second chamber 55″ contracts and closed asthe volume of the second chamber 55″ expands in the manner of FIGS. 5and 6. Consequently and to the extent any refrigerant and/orcontaminants collect in the chamber 55″, they will be captured anddirected harmlessly back through the one-way exhaust line 61″ into theincoming refrigerant line 7′ and out the discharge line 15′. Theundesirable refrigerant and/or contaminants in this regard like theearlier embodiments are positively pumped into the incoming line 7′ asthe pressure in the contracting second chamber 55′″ exceeds the linepressure of 7′.

To aid in discharging these undesirable fluids and with the fixed axis25″ extending substantially horizontally as in FIG. 11, the inlet to theexhaust line 61″ preferably extends as shown from the second chamber 55″substantially at the lowest location of the second chamber 55″ relativeto the fixed axis 25″. Gravity as in the earlier embodiments can thenhelp in collecting and delivering the contaminants into the exhaust line61″ particularly at the start up of the recovery unit and during itsoperation. The flow through the exhaust line 61″ also serves to reducethe pressure load on the piston rod seal 54″ in FIG. 11 to furtherensure that no contaminants pass thereby and that the scotch yokearrangement 31″ remains isolated from any such exposure. In this regardas in the earlier embodiments, the second end wall 53″ of the secondchamber 55″ slidably and sealingly at 54″ receives the reciprocatingpiston rod 23″ therethrough. As discussed above, the piston rod seal at54″ then aids in isolating the scotch yoke arrangement 31 from thesecond chamber 55″ and its contents. It is noted that the first andsecond side wall portions 35″ and 57″ of the cylinder 33″ as in theearlier embodiments are adjacent one another along the axis 25″. Theseportions can be spaced from each other as shown or can overlap oneanother if desired. The piston underside 51″ is preferably parallel tothe outer piston surface 47″. Flow through the single piston compressor11″ of FIG. 11 is then past the valve 43″ in the first chamber inlet 39″into the first chamber 49″ and out the valve 45″ in the first chamberoutlet 41″. The operation of the scotch yoke arrangement 31″ asindicated above is essentially the same as in the earlier embodiments.

The above disclosure sets forth a number of embodiments of the presentinvention described in detail with respect to the accompanying drawings.Those skilled in this art will appreciate that various changes,modifications, other structural arrangements, and other embodimentscould be practiced under the teachings of the present invention withoutdeparting from the scope of this invention as set forth in the followingclaims. In particular, it is noted that the word substantially isutilized herein to represent the inherent degree of uncertainty that maybe attributed to any quantitative comparison, value, measurement orother representation. This term is also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter involved.

We claim:
 1. A portable, refrigerant recovery unit for transferringrefrigerant from a refrigeration system to a storage tank, said recoveryunit including: first and second piston heads (21,21′) respectivelyrigidly attached to first and second piston rods (23,23′), said pistonrods extending along a common fixed axis (25) and being respectivelyrigidly attached to a yoke member (29) of a scotch yoke arrangement (31)to extend in opposite directions along said common fixed axis (25), saidscotch yoke arrangement (31) translating rotational motion of a drivingmember into reciprocal movement of said yoke member (29) and rigidlyattached piston rods (23,23′) and piston heads (21,21′) along saidcommon fixed axis (25), each piston head being slidably and sealinglyreceived in a cylinder (33,33′) having a first side wall portion(35,35′) and a first end wall (37,37′), said first end wall having aninlet (39,39′) and outlet (41,41′) therethrough with respective one-wayvalves (43,43′ and 45,45′) therein, each piston head having an outersurface (47,47′) opposing said first end wall to define a first chamber(49,49′) with said first end wall (37,37′) and said first side wallportion (35,35′) of said cylinder (33,33′), said recovery unit furtherincluding incoming lines (7,7′) in fluid communication with each otherand each inlet of each first chamber upstream of the valve in eachinlet, said incoming lines additionally being in fluid communicationwith the refrigerant in said refrigeration system, each reciprocatingpiston rod (23,23′) moving the respective piston head (21,21′) alongsaid common fixed axis (25) relative to each first end wall (37,37′)between first and second positions to respectively expand the volume ofthe first chamber (49,49′) to receive refrigerant from saidrefrigeration system into said first chamber and to contract the volumeof the first chamber to drive said refrigerant out of said firstchamber, each piston head being in the respective first and secondpositions when the other piston head is in the respective second andfirst positions wherein any opposing forces (F,F′) exerted by therefrigerant on the respective outer surfaces (47,47′) of the pistonheads (21,21′) along the common fixed axis (25) counterbalance oneanother, each piston head (21,21′) further having an underside (51,51)adjacent the piston rod (23,23′) attached to the piston head (21,21′)and extending about the piston rod and outwardly of the common fixedaxis (25), said recovery unit further including second end walls(53,53′) respectively opposing the undersides (51,51′) of the respectivepiston heads (21,21′) to define a respective second chamber (55,55′)with the respective underside (51,51′) and a respective second side wallportion (57,57′) of the respective cylinder (33,33′), each piston rod(23,23′) being respectively slidably and sealingly received in therespective second end wall (53,53′), said recovery unit further having arespective exhaust line (61,61′) extending between the respective secondchamber (55,55′) and the respective incoming line (7,7′), each exhaustline (61,61′) having a one-way valve (63,63′) therein to restrict flowthrough the respective exhaust line (61,61′) to one direction from therespective second chamber (55,55′) to the respective incoming line(7,7′) wherein each reciprocating piston rod (23,23′) moves therespective piston head (21,21′) along the common fixed axis (25)relative to the respective first end wall (37,37′) of the respectivecylinder (33,33′) between said first and second positions torespectively contract and expand the volume of the respective secondchamber (55,55′), said one-way valve (63,63′) in said respective exhaustline (61,61′) being opened as the volume of the respective secondchamber (55,55′) contracts and closed as the volume of the respectivesecond chamber (55,55′) expands.
 2. The recovery unit of claim 1 whereinthe outer surfaces (47,47′) of the piston heads (21,21′) and therespective undersides (51,51′) of the piston heads (21,21′) aresubstantially parallel to each other.
 3. The recovery unit of claim 1wherein the first and second side wall portions (35,57 and 35′,57′) ofthe respective cylinders (33,33′) are substantially adjacent one anotheralong said common fixed axis (25).
 4. The recovery unit of claim 1wherein the first and second side wall portions (35,57 and 35′,57′) ofthe respective cylinders (33,33′) are spaced from one another along saidcommon fixed axis (25).
 5. The recovery unit of claim 1 wherein thecommon fixed axis (25) extends substantially horizontally and eachrespective exhaust line (61,61′) has an inlet extending from therespective second chamber (55,55′) substantially at the lowest locationof the respective second chamber (55,55′) relative to the common fixedaxis (25).
 6. The recovery unit of claim 1 wherein the outer surfaces(47,47′) of said piston heads (21,21′) have substantially the same areaand the undersides (51,51′) of said piston heads (21,21′) havesubstantially the same area.
 7. The recovery unit of claim 1 whereinsaid refrigerant in said incoming lines (7,7′) is above atmosphericpressure.
 8. The recovery unit of claim 7 wherein said scotch yokearrangement is isolated from exposure to said second chambers (55,55′)and said refrigerant.
 9. The recovery unit of claim 1 wherein thepressure of the refrigerant in the incoming lines (7,7′) is the same andthe inlet valves (43,43 ¹) of said first chambers (49,49′) upstream ofthe inlets are simultaneously and continuously exposed to said samepressure.
 10. The recovery unit of claim 1 wherein the pressure of therefrigerant in the incoming lines (7,7′) varies over time and the inletvalves (43,43 ¹) of said first chambers (49,49′) upstream of the inletsare simultaneously and continuously exposed to said varying refrigerantpressure.
 11. The recovery unit of claim 1 wherein the respective firstend walls (37,37′) and outer surfaces (47,47′) of the piston heads(21,21′) are substantially planar and substantially parallel to eachother.
 12. The recovery unit of claim 11 wherein the respective firstend wall and outer surface of each piston head are substantially flushwith each other in the respective second position of said piston head.13. The recovery unit of claim 1 further including outgoing lines(15,15′) in respective fluid communication with each other downstream ofthe valve (45,45′) in each outlet (41,41′) of each first chamber(49,49′), said outgoing lines (15,15′) additionally being in fluidcommunication with said storage tank (4).
 14. The recovery unit of claim1 wherein the rotational motion of said driving member is about an axis(24) substantially perpendicular to the common fixed axis (25).
 15. Aportable, refrigerant recovery unit for transferring refrigerant from arefrigeration system to a storage tank, said recovery unit including: atleast one piston head rigidly attached to a piston rod, said piston rodextending along a fixed axis and being rigidly attached to a yoke memberof a scotch yoke arrangement, said scotch yoke arrangement translatingrotational motion of a driving member into reciprocal movement of saidyoke member and rigidly attached piston rod and piston head along saidfixed axis, said piston head being slidably and sealingly received in acylinder having a first side wall portion and a first end wall, saidfirst end wall having an inlet and outlet therethrough with respectiveone-way valves therein, said piston head having an outer surfaceopposing said first end wall to define a first chamber with said firstend wall and said first side wall portion of said cylinder, saidrecovery unit further including at least one incoming line in fluidcommunication with said inlet of said first chamber upstream of thevalve in said inlet, said incoming line additionally being in fluidcommunication with the refrigerant in said refrigeration system, saidreciprocating piston rod moving the piston head along said fixed axisrelative to said first end wall between first and second positions torespectively expand the volume of the first chamber to receiverefrigerant from said refrigeration system into said first chamber andto contract the volume of the first chamber to drive said refrigerantout of said first chamber, said piston head further having an undersideadjacent the piston rod attached to the piston head and extending aboutthe piston rod and outwardly of the fixed axis, said recovery unitfurther including a second end wall opposing the underside of the pistonhead to define a second chamber with the underside and a second sidewall portion of the cylinder, said piston rod being slidably andsealingly received in the second end wall, said recovery unit furtherhaving at least one exhaust line extending between the second chamberand the incoming line, said exhaust line having a one-way valve thereinto restrict flow through the exhaust line to one direction from thesecond chamber to the incoming line wherein said reciprocating pistonrod moves the piston head along the fixed axis relative to the first endwall of the cylinder between said first and second positions to contractand expand the volume of the second chamber, said one-way valve in saidexhaust line being opened as the volume of the second chamber contractsand closed as the volume of the respective second chamber expands. 16.The recovery unit of claim 15 wherein the outer surface of the pistonhead and the underside of the piston head are substantially parallel toeach other.
 17. The recovery unit of claim 15 wherein the first andsecond side wall portions of the cylinder are substantially adjacent oneanother along said fixed axis.
 18. The recovery unit of claim 15 whereinthe first and second side wall portions of the cylinder are spaced fromone another along said fixed axis.
 19. The recovery unit of claim 15wherein the fixed axis extends substantially horizontally and saidexhaust line has an inlet extending from the second chambersubstantially at the lowest location of the second chamber relative tothe fixed axis.
 20. The recovery unit of claim 15 wherein saidrefrigerant in said incoming line is above atmospheric pressure.
 21. Therecovery unit of claim 20 wherein said scotch yoke arrangement isisolated from exposure to said second chamber and said refrigerant. 22.The recovery unit of claim 15 wherein the first end wall and outersurface of the piston head are substantially planar and substantiallyparallel to each other.
 23. The recovery unit of claim 22 wherein thefirst end wall and outer surface of said piston head are substantiallyflush with each other in the second position of said piston head. 24.The recovery unit of claim 15 wherein the rotational motion of saiddriving member is about an axis substantially perpendicular to the fixedaxis.
 25. The recovery unit of claim 15 wherein the recovery unit hasonly one piston head and one piston rod.